It is well known that conventional concretes such as silicious concretes have, and this for an extremely short time, only a very slight capacity for being shaped after demolding. Because of this, the hardening times do not permit using complicated moldings for reworking. This very low capability for shaping requires the design and production of moldings or molds which are extremely sophisticated so as to permit reproductions of shape or of architectural molding. On the other hand, for economical reasons, it is very often necessary to consider the employment of framework or molds requiring series which, in the case of the ornamentation of facades, harden in repetitions of shaped modules.
In the field of concrete, there has already been used granulated limestone to give to the concrete individual characteristics different from those of silicious concretes.
Thus, the patent FR-A-2.520.349 describes a process for the production of an artificial or synthetic stone using successively the steps of:
mixing the ingredients: PA1 casting in molds PA1 demolding PA1 hardening (naturally) PA1 sand blasting (adapted to imitate the external appearance of a natural stone). PA1 White cement from 10 to 40%, preferably 22 to 28% PA1 Limestone in granulated form and if desired PA1 powder, 40 to 80%, preferably 60 to 66% PA1 Water 5 to 50%, preferably 11% PA1 Plasticizer 0 to 5%, preferably 1% that is mixed in a horizontal mixer, before compacting by tamping within the molds, or by liquid pouring into the molds which are then vibrated manually or even mechanically. This process is distinguished from the invention by its step of vibrating which, in the case of the process of the invention, is strongly discouraged because it gives rise to segregation of the elements entering into the composition of the concrete rendering the latter useless for all shaping, demolding, cutting and sculpting in contrast to all the conventional processes in which the vibration gives rise to the binding of the various elements. This observation is applicable in the same way to the patent FR-A-2.414.028. PA1 a volume V1 of binder which is 20 to 60% of V PA1 a volume V2 of high hardness filler which is 0 to 40% of V and PA1 a volume V3 of water which is 30 to 80% of V. PA1 20%.times.V.ltoreq.V1.ltoreq.60%.times.V PA1 0%.times.V.ltoreq.V2.ltoreq.40%.times.V PA1 30%.times.V.ltoreq.V3.ltoreq.90% x v (A) PA1 50%.times.VT.ltoreq.V+V3.ltoreq.90%.times.VT
limestone sand; 18 to 24% PA2 silicious sand; 35 to 45% PA2 white lime and cement; 33 to 40% PA2 water
This artificial stone is distinguished from that of the invention by its content of silica and a hydraulic binder which do not permit slow hardening of the assembly as well as by the quantity of water which, in a just sufficient quantity, is equivalent to about 10% by volume of the total volume. Similarly, the molding process, which requires the drying of the product at a temperature of 35.degree. to 40.degree. C., differs from the molding process generally used in the framework of the present invention.
The patent FR-A-2.584.707 describes itself a process for production of a reconstituted limestone characterized by the fact that it consists in preparing a mixture of:
Finally, the patents FR-A-1.291.011 and 1.248.052 describe an artificial stone and an agglomerate which, although having similar compositions to those of the concrete of the present invention, do not have the essential characteristics of this latter by reason of the portions of the completely different components and of the lack of use of the specific limestones.